This invention relates to amorphous metallic materials, and, more particularly, to an amorphous metallic article having an extended surface area.
The exact morphology of the surface of a solid plays a key role in determining many of its properties. For example, strength, corrosion resistance, ability to be joined to other materials, and electrical and magnetic properties can all be dependent upon the characteristics of surfaces, as can many other properties. The total area of surface present is also important, as the rate of a reaction involving a metal may be limited by the total contact area between the metal and a reactant.
A catalyst is a metal or other material that aids in the accomplishing of a chemical reaction, without itself entering into the chemical reaction. As an example, platinum catalysts are utilized in automobile catalytic converters to transform polluting gasses to less harmful gasses. Two characteristics of catalysts, their total surface area and the atomic configuration of the surface, often determine and control their success in promoting a reaction. It is generally preferred that a maximum amount of surface area be available, and therefore catalysts are often provided in the form of very fine particles having a large surface-to-volume ratio. It is also observed that the precise arrangement of the atoms on a surface and the interatomic spacing of the atoms can influence catalysis, and in particular some crystallographic planes of crystalline catalysts are more effective then others in promoting catalysis.
In recent years, it has been recognized that amorphous, or non-crystalline, materials can promote catalysis. The metallic atoms in an amorphous material exhibit no long-range order, and therefore the atoms are not arranged on a crystallographic lattice. It is believed that this lack of crystallographic arrangement imparts improved catalytic properties to the material. Since amorphous materials of various potentially useful compositions can now be formed by known techniques, there has developed a need for amorphous materials in forms having large amounts of surface area per unit volume.
Amorphous materials are often formed as small particles, usually spherical in shape, by rapid quenching from the melt. While these particles inherently have relatively high surface-to-volume ratio, they are often inconvenient to handle in a bulk form and necessitate the use of complex container arrangements to allow contact between the amorphous material and the chemical reactants, when the amorphous material is to be used as a catalyst. Other approaches to preparing amorphous materials, such as the solidification of ribbons, electrodeposition, vapor deposition, or sputtering result in pieces of amorphous material which are more easily handled but which do not have the desired high surface area.
In another approach directed toward providing a catalyst, it has been proposed to prepare a hybrid amorphous material having regions of a local order non-equilibrium structure, and then to preferentially remove the atoms in these regions which are at a surface. This technique is said to produce a roughening of the surface, thereby increasing the surface area by a relatively small amount and modifying the atomic structure at the surface. This approach does not produce an extended three-dimensional structure having internal passageways for extensively increased surface area.
Accordingly, there exists a need for amorphous materials having extended surface areas to produce a high surface-to-volume ratio, but which are monolithic and therefore do not require special containment systems or are in finely divided form. A variety of applications can be envisioned for such materials, including, for example, catalysts and membranes used as filters or in osmosis. The present invention fulfills this need, and further provides related advantages.